To unlink a PDF from an index, press and hold the Index entry to display the Select Index Action menu, choose Unlink From Index, choose Yes to perform the unlink. The PDF that was linked to the index is renamed as follows:

YYMMDD-HHMMSS(year month day - hours minutes seconds)-Index Name

If you were to select Unlink From Index for Classic Real Book you would wind up with the following PDF file in the My Scores view: